Fix incremental .mar creation for esr78

#40026 (closed) fixed the full .mar creation for esr78. We need to fix up our perl script for creating proper incremental .mar files as well.

changed milestone to %Tor Browser: 10.0

added 1 deleted label

assigned to @gk

changed time estimate to 1h

added Doing label

mentioned in issue #34227 (closed)

mentioned in merge request !17 (closed)

mentioned in merge request tor-browser!14 (merged)

mentioned in issue #40032 (closed)

mentioned in merge request !18 (merged)

closed via merge request !18 (merged)

mentioned in issue #40045 (closed)

mentioned in merge request !38 (merged)